Method of carbon chain extension using novel aldol reaction

ABSTRACT

Method of producing C 8 -C 15  hydrocarbons. comprising providing a ketone starting material; providing an aldol starting material comprising chloromethylfurfural; mixing the ketone starting material and the aldol starting material in a reaction in the presence of a proline-containing catalyst selected from the group consisting of Zn(Pro) 2 , Yb(Pro) 3 , and combinations thereof, or a catalyst having one of the structures (I), (II) or (III), and in the presence of a solvent, wherein the solvent comprises water and is substantially free of organic solvents, where (I), (II) and (III) respectively are: 
     
       
         
         
             
             
         
       
         
         
           
             where R 1  is a C 1 -C 6  alkyl moiety, X=(OH) and n=2. 
           
         
       
    
     
       
         
         
             
             
         
       
     
     In (III), X may be CH 2 , sulfur or selenium, M may be Zn, Mg, or a lanthanide, and R 1  and R 2  each independently may be a methyl, ethyl, phenyl moiety.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/542,384, filed Aug. 17, 2009, the entirety of which is incorporatedby reference herein.

STATEMENT OF FEDERAL RIGHTS

The United States government has rights in this invention pursuant toContract No. DE-AC52-06NA25396 between the United States Department ofEnergy and Los Alamos National Security, LLC for the operation of LosAlamos National Laboratory.

FIELD OF THE INVENTION

The present invention relates to methods of producing C₈-C₁₅hydrocarbons from renewable feedstocks such as cellulosics, sugars andglycerin, by means of an organo-catalyzed aldol reaction.

BACKGROUND OF THE INVENTION

Development of sustainable methods of making transportation fuels andchemical feedstocks such as surfactants from renewable resources isbecoming increasingly important, due to the desirability of decreasingdependence on petroleum resources. Carbohydrates obtained from biomassare renewable and readily available, and there has been much focus onproducing fuel and other useful materials from biomass-derived startingmaterials. Other readily available starting materials include simplesugars, glycerol and the oxidation product of glycerol, dihydroxyacetone(DHA). Compounds suitable for use as chemical feedstocks generallyinclude C₈-C₁₅ alcohols and olefins. Commercially useful surfactants maycomprise from about 10 to about 22 carbon atoms. Therefore, in order toproduce surfactants from biomass-derived starting materials, the carbonchain length of the starting material must be increased. One commonmethod of achieving this is through the aldol reaction, which forms acarbon-carbon bond between an aldehyde and a ketone. Cellulosics, sugarsand glycerin can readily be converted to suitable reagents for the aldolreaction. For example, cellulose and glucose can be converted tohydroxymethylfurfural (HMF). Dihydroxyacetone can be formed fromglycerol.

Use of the aldol reaction with reagents derivable from cellulosics andsugars has been described previously (see, e.g., Huber et al., Science,vol. 208, Jun. 3, 2005, pp. 1446-1450). However, the reactions resultedin a range of carbon chain lengths, and thus exhibited poor selectivity.In addition, the reactions required high temperatures (approximately100° C.), and the use of an organic solvent in addition to water. Mostimportant, the reaction was shown to be unsuccessful with ketonereagents other than acetone. All of these factors contribute to makingthe process less suitable for large-scale industrial use.

The use of a zinc-proline (Zn(Pro)₂) catalyst has been shown to besuccessful in certain types of aldol reactions, and addresses some ofthe above drawbacks. Zinc-proline catalysts result in higherselectivity, and have been shown to work with DHA as a ketone reagent.To date, however, zinc-proline catalysts have shown only to successfullycatalyze reactions between ketones and aromatic aldehydes (for example,benzaldehydes) and not between ketones and reagents derived from biomasssources, such as HMF. Although able to catalyze reactions in aqueoussolvents and at lower temperatures, the reactions described to dateusing zinc-proline catalysts have required the addition of an organicco-solvent, such as tetrahydrofuran (THF).

There exists a need, therefore, for a method of increasing carbon chainlength via the aldol reaction that utilizes reagents derived frombiomass sources, is highly selective, can be performed at roomtemperature and does not require the use of an organic co-solvent, thusmaking the process more suitable for large-scale production withspecificity. There exists a further need for additional catalysts thatallow the aldol reaction to proceed under conditions suitable forlarge-scale use.

SUMMARY OF THE INVENTION

The present invention meets the aforementioned needs by providing amethod of increasing carbon chain length by utilizing the aldol reactionthat can be performed with either zinc-proline, ytterbium-proline, ormetal chelated N-(2-hydroxy-2-methylpropyl)pyrrolidine-2-carboxamidebased catalysts, and which can be performed at room temperature usingonly water as the solvent. The reaction utilizes DHA (and other ketonesor aldehydes) as the ketone reagent and chloromethylfurfural as thealdehyde reagent, which can be obtained from biomass cellulosics. Thereaction has high specificity, and results in formation of(E)-4-(5-(chloromethyl)furan-2-yl)but-3-en-2-one,(1E,4E)-1,5-bis(5-(chloromethyl)furan-2-yl)penta-1,4-dien-3-one,3,4-dihydroxy-4-(5-(chloro-methyl)furan-2-yl)butan-2-one,(E)-5-(5-(chloromethyl)furan-2-yl)-4,5-dihydroxy-1-(5-(hydroxymethyl)furan-2-yl)pent-1-en-3-oneand/or 1,3,4-trihydroxy-4-(5-(chloromethyl)furan-2-yl)butan-2-one, witha yield of 60%.

The following describe some non-limiting embodiments of the presentinvention.

According to one embodiment of the present invention, a method ofproducing C₈-C₁₅ hydrocarbons is provided, comprising providing a ketonestarting material; providing an aldol starting material comprisingchloromethylfurfural; and mixing the ketone starting material and thealdol starting material in a reaction in the presence of aproline-containing catalyst selected from the group consisting ofZn(Pro)₂, Yb(Pro)₃, and combinations thereof, and a solvent, wherein thesolvent comprises water and is substantially free of organic solvents,to produce the C₈-C₁₅ hydrocarbons.

According to another embodiment of the present invention, a method ofproducing C₈-C₁₅ hydrocarbons is provided, comprising providing a ketonestarting material; providing an aldol starting material; and mixing theketone starting material and the aldol starting material in a reactionin the presence of a catalyst having the structure:

and a solvent, wherein the solvent comprises water and is substantiallyfree of organic solvents, to produce the C₈-C₁₅ hydrocarbons.

According to yet another embodiment of the present invention, a methodof producing C₈-C₁₅ hydrocarbons is provided, comprising providing aketone starting material; providing an aldol starting material; andmixing the ketone starting material and the aldol starting material in areaction in the presence of a catalyst having the structure:

wherein R is a C₁-C₆ alkyl moiety, X=(OH) and n=2, and in the presenceof a solvent, wherein the solvent comprises water and is substantiallyfree of organic solvents, to produce the C₈-C₁₅ hydrocarbons.

According to yet another embodiment of the present invention, a methodof producing C₈-C₁₅ hydrocarbons is provided, comprising providing aketone starting material; providing an aldol starting material; andmixing the ketone starting material and the aldol starting material in areaction in the presence of a catalyst having the structure:

where X is CH₂, sulfur or selenium, M is Zn, Mg, or a lanthanide, and R₁and R₂ each independently are a methyl, ethyl, or phenyl moiety; and inthe presence of a solvent, wherein the solvent comprises water and issubstantially free of organic solvents, to produce the C₈-C₁₅hydrocarbons.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a) and (b) depict exemplary reaction schemes of the presentinvention, wherein chloromethylfurfural(5-(chloromethyl)furan-2-carbaldehyde) reacts with acetone (FIG. 1( a),one molar equivalent and FIG. 1( b), 0.5 molar equivalents) to form thehydrocarbon products (E)-4-(5-(chloromethyl)furan-2-yl)but-3-en-2-oneand (1E,4E)-1,5-bis(5-(chloromethyl)furan-2-yl)penta-1,4-dien-3-one.

FIG. 2 depicts the reaction between chloromethylfurfural withhydroxyacetone to form the hydrocarbon product4-(5-(chloromethyl)furan-2-yl)-3,4-dihydroxybutan-2-one.

FIG. 3 depicts the reaction of4-(5-(chloromethyl)furan-2-yl)-3,4-dihydroxybutan-2-one with5-(hydroxymethyl)furan-2-carbaldehyde to form the C₁₅ hydrocarbon(E)-5-(5-(chloromethyl)furan-2-yl)-4,5-dihydroxy-1-(5-(hydroxymethyl)furan-2-yl)pent-1-en-3-one.

FIG. 4 depicts the reaction of dihydroxyacetone withchloromethylfurfural to form the hydrocarbon product4-(5-(chloromethyl)furan-2-yl)-1,3,4-trihydroxybutan-2-one.

DETAILED DESCRIPTION OF THE INVENTION

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention. To the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

The present invention relates to a method of producing C₈-C₁₅hydrocarbons by increasing the carbon chain length of carbohydrates,which may be derived from herbaceous and woody biomass. As used herein,“hydrocarbons” is understood to include alcohols, olefins, ketones andother compounds comprising carbon, hydrogen and oxygen (as depicted inFIGS. 1-4), and is not intended to mean only compounds consisting ofcarbon and hydrogen atoms. Suitable reagents may be obtained fromabundant chemical feedstocks such as glycerin. The method results inproduction of C₈-C₁₅ hydrocarbons, which may be subsequentlyhydrogenated and dehydrated to produce, among other compounds,transportation fuels and surfactants. The method utilizes the aldolreaction, also known as the aldol condensation reaction, which forms acarbon-carbon bond between an aldehyde and a ketone (herein referred toas an “aldehyde reagent” and a “ketone reagent,” respectively).

Aldehyde reagents suitable for use in the present invention include, butare not limited to, chloromethylfurfural (CMF, CAS #1623-88-7) andfuran-2-carbaldehyde. Other halide-substituted methylfurfurals also maybe suitable, such as bromomethylfurfural and iodomethylfurfural. Thecarbon atom adjacent to the halide-substituted methyl group allowsconversion to desirable alcohol and olefin end products. In addition,cellulose may also be converted directly to chloromethylfurfural, asdescribed in Mascal et al., Angew. Chem. Int. Ed., 47, pp 7924-7926(2008). Suitable ketone reagents in the present invention includeacetone, dihydroxyacetone (DHA), methylacetoacetate, ethylacetoacetate,and combinations thereof.

The reaction of the aldehyde and ketone reagents proceeds in thepresence of a suitable catalyst. A suitable catalyst must allow thereaction to proceed at room temperature, with water as a solvent, andresult in a selectively high yield of the desired product. One suitablecatalyst of the present invention is Zn(Proline)₂, which may have thefollowing structure:

Another suitable catalyst is Yb(Proline)₃, or Yb(Pro)₃, which has astructure similar to Zn(Proline)₂, wherein the Zn is replaced by Yb.

Other suitable catalysts include the following structures (I), (II) and(III):

where R₁ is a C₁-C₆ alkyl moiety, where “alkyl” is understood to mean asubstituted or unsubstituted alkane, alkene or alkyne, X=(OH) and n=2.

In (III), X may be CH₂, sulfur or selenium, M may be Zn, Mg, or alanthanide, and R₁ and R₂ each independently may be a methyl, ethyl,phenyl moiety. It is to be understood that the phenyl group may compriseheteroatoms such as nitrogen or oxygen, provided that the atoms in R₁ orR₂ which are closest to theN-(2-hydroxy-2-methylpropyl)pyrrolidine-2-carboxamide core structure area CH₂ group. In one embodiment, the reaction is performed in a solventwhich comprises water and is substantially free of organic solvents. By“substantially free of organic solvents” is meant that the amount oforganic solvent is about 1% or less. By “organic solvent” organicsolvents other than water or salts that would be understood by one ofskill in the art to be used in synthesis reactions, including but notlimited to dimethylformamide (DMF), tetrahydrofuran (THF), alcohols,etc. The solvent further may comprise a salt, brine, saturated sodiumchloride, or natural waters comprising salts. The reaction may beperformed at room temperature (25° C.), and alternatively at atemperature of from about 0° C. to about 100° C. The reaction may have ayield of at least 60%, alternatively of at least 75%, alternatively ofat least 90%, and alternatively of at least 99%. The reaction sequencecan be tuned to give desired fuel properties by reaction with, forexample, the DHA-furan complex, by employing selective regiochemistry.

EXAMPLES Example 1

The reactions are performed in water without adjustment of pH.Piperidine was used in 5 mol %. Chloromethylfurfural (CMF) (0.631 g,5.00 mmol) is charged in a small round bottom flask with a stirring bar,water (4.0 mL) is added. Acetone (0.290 g, 5.00 mmol (1 equivalent) or0.25 mmol (0.5 equivalent) is then added (FIG. 1). The mixture is thenstirred while piperidine was added at room temperature. The reactionmixture is kept closed with a plastic cap and stirred for 20 hrs. Thestirring bar is removed and silica gel added. The mixture is dried withrotary evaporation. The residue is loaded on silica gel and eluted with50% ethyl acetate in hexanes. Di-CMF adduct also is produced.

As would be understood by one of skill in the art, substitution ofreagents as shown in FIGS. 1-4 under similar reaction conditions resultsin the products depicted in FIGS. 1-4.

Example 2

In a 100 mL single-necked round bottom flask was placed HOBT(hydroxybenzotriazole) (1.95 g), L-Boc-proline (3.00 g), and2-hydroxy-2-methyl-propyl-1-amine. To this was added 70 mL of anhydrousacetonitrile. This was stirred until homogenous and then chilled to 0°C. The EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide), (3.20 g) wasadded in one portion to this mixture. The mixture was allowed to warm toroom temperature and stirred overnight. The solvent was removed invacuo. The remaining material was then taken up in 60 mL of methylenechloride and subsequently washed 4× with 10 mL of 5% citric acid. Thesuspension was filtered and dried over sodium sulfate. Filtration andremoval of the solvent gave rise to the crude material. Purification bysilica gel chromatography using 10% methanol/methylene chloride aseluent afforded 3.0336 g of an amide having the structure (IV),tert-butyl2-(2-hydroxy-2-methylpropylcarbamoyl)pyrrolidine-1-carboxylate. ¹H NMR(CDCl₃) d 4.29 (J=4.2 Hz, 1H), 3.45 (m, 2H), 3.26 (m 2H), 1.92 (m, 2H),1.62 (m, 2H), 1.47 (s, 9H), 1.22 (s, 6H).

Whereas particular embodiments of the present invention have beenillustrated and described, it would be clear to those skilled in the artthat various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A method of producing a C₈-C₁₅ hydrocarboncomprising: a) providing a ketone starting material; b) providing analdol starting material comprising chloromethylfurfural; and c) mixingthe ketone starting material and the aldol starting material in areaction in the presence of a piperidine-containing catalyst and asolvent, wherein the solvent comprises water that is substantially freeof organic solvents, to produce the C₈-C₁₅ hydrocarbon.
 2. The method ofclaim 1, wherein the ketone starting material comprises acetone,dihydroxyacetone, or combinations thereof.
 3. The method of claim 1,wherein the reaction occurs at about 25° C.
 4. The method of claim 1,wherein the solvent further comprises a salt.
 5. The method of claim 1,further comprising hydrogenating and dehydrating the C₈-C₁₅ hydrocarbon.